Gaining inspiration from perspiration

PHILADELPHIA -- First the gym class had a 20-minute workout. Treadmills. Weightlifting. Very strenuous.

Then researchers at Pennsylvania State University's suburban campus in Lima stuck tiny test tubes under the subjects' armpits and collected samples of sweat.

"They couldn't use deodorants, so they started to smell horrible," recalled Mary Varano, a nursing student on the research team.

The experiment produced a few giggles -- hey, some people are ticklish under there. But it had a serious educational purpose: The researchers found no difference in the pH, or degree of acidity, of male and female sweat.

That could have important implications, said John Tierney, a Penn State chemistry professor.

He and his collaborators also found that the pH of sweat is dramatically affected by certain medications, so it may be possible to develop a simple spot test for the presence of drugs in athletes.

How did all this start?

More than a year ago, Mr. Tierney asked a class of students with non-science majors where they might have heard the term pH. Television commercials, came the answer. Nearly everyone knew, for example, that Secret anti-perspirant was "pH-balanced, so it was "strong enough for a man, but made for a woman."

That sounded nice, a sort of high-tech version of the Victorian notion that horses sweat, men perspire, but women, those delicate creatures, glow. But it struck Mr. Tierney as wrong. Why should a man's sweat be more or less acidic than a woman's?

A competitive rower (he is now in Europe managing the Olympic rowing team), Mr. Tierney has had plenty of experience with sweat, but he couldn't come up with any research to prove he was right. He enlisted a campus librarian, who also could find nothing.

"She spent a lot of time searching data bases and medical literature," Mr. Tierney said recently from Belgium. "There was very limited information. I was expecting to see tons."

Mr. Tierney also talked to officials at Procter & Gamble Co., maker of Secret (and Sure and Old Spice). The company insisted that its research showed that female sweat was less acidic than that of men, but the details were, er, secret.

(Procter & Gamble spokesman Donald Tassone responded to a reporter's query with a fax. It explained that women's sweat is less acidic than men's and that the pH of Secret's active ingredient was adjusted accordingly to provide "excellent wetness protection," without irritating the skin. That's what "pH-balanced" means.)

So Mr. Tierney headed for the gymnasium. Using three tests -- pH paper test strips that changed color, a chemical solution that also changed color and a calibrated electronic pH meter -- he and his helpers examined the sweat of 20 men and 20 women. Their finding: Normal sweat has a pH of 6.1 to 6.7, regardless of sex.

The only big variation was with three students who turned out to be taking antibiotics -- which led Mr. Tierney to theorize that forbidden drugs, such as cocaine or steroids, might also affect sweat pH.

Someone somewhere may already be testing that theory, "but we haven't found it in the literature," Mr. Tierney said.